Analysis of aerosol particles by mass spectrometry provides useful information on the composition of the sample. For example, polluted air in cities may be sampled and analyzed to determine the source of pollutants in the city air. Lee et al., “Determination of the size distribution of polydisperse nanoparticles with single-particle mass spectrometry: The role of ion kinetic energy,” AEROSOL SCIENCE AND TECHNOLOGY 39 (2): 162-169 February (2005), provides an exemplary instrumentation that may be employed to analyze the composition of aerosol particles. In this example, a single-particle mass spectrometer (SPMS) consists of an aerodynamic inlet region, a source region for particle-to-ions conversion with a free-firing pulsed laser, and a detector. Because the chamber which houses both the flight tube and the ionization region has a pressure of about 6×10−7 Torr during the operation, the distribution of detected ions is determined by the composition and morphology of the particle and the dynamics of the ablation and mass analysis processes.
Reents et al., “Simultaneous elemental composition and size distributions of submicron particles in real time using laser atomization/ionization mass spectrometry,” AEROSOL SCIENCE AND TECHNOLOGY 33:122-134 July-August (2000) discloses use of “dried” particles that are provided employing desiccated molecular sieves. Particles were introduced into the aerosol mass spectrometer, atomized and cationized by an intense laser beam, and the nascent ions were analyzed by a time-of-flight mass spectrometer. Because the mass spectrometer needs to operate in high vacuum (<1.0×10−6 Torr), only a minute portion of the created ions were sampled through the mass analyzer. The distribution of ions sampled into the analyzer depends on the composition and morphology of the individual particle and the dynamics of the ablation process. Consequently, the measured ion distribution does not necessarily correlate with the elemental composition of the particle. This is especially true when the particle has a non-homogeneous composition and morphology. Additionally, the mass analysis can only be performed one time per laser ablation event.
Thus, the prior art instrumentation requires ablation of aerosol particles at an high vacuum environment, and thereby limits the purity and composition of particles that may be analyzed effectively. Such a limitation practically prevents reliable real-time analysis of particles in an environment in which the composition, morphology and purity varies on an individual particle basis.
In view of the above, there exists a need for instrumentation for providing precise compositional analysis of individual aerosol particles. Particularly, there exists a need for a real-time particle analyzer that provides elemental composition analysis of particles sampled from the air or surfaces in real time.